The pilot and sole occupant of a helicopter that crashed at Birchwood Airport in May 2014 likely lost control of the aircraft after experiencing a "sudden, acute cardiac event," the National Transportation Safety Board said in a final report on the accident published this week.Tom Moore, 62, of Anchorage, was flying the Robinson R44 helicopter, practicing maneuvers with an external load. Moore was using a 150-foot long-line and weighted barrel. It was one of several similar practice flights Moore had conducted, the federal agency said."Although the accident pilot's workload was increased by the demands of maintaining traffic separation and communicating on the radio in the busy, non-towered airport environment, there was no evidence to suggest that such...